Non-transitive equals passes

[GoogleCodeExporter]

Consider this class:

public final class School {
    private final String name;
    private final String nickname;

    public School(String name, String nickname) {
        this.name = name;
        this.nickname = nickname;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof School)) {
            return false;
        }
        School other = (School)obj;
        return nullSafeEqual(name, other.name) ||
                nullSafeEqual(nickname, other.nickname);
    }

    private boolean nullSafeEqual(String a, String b) {
        return a == null ? b == null : a.equals(b);
    }

    @Override
    public int hashCode() {
        return 42;
    }

    @Override
    public String toString() {
        return "School: name=" + name + ", nickname=" + nickname;
    }
}

This equals method is non-transitive, as the following code demonstrates:

School red = new School("A", "1");
School green = new School("A", "2");
School blue = new School("B", "2");

assertTrue(red.equals(green));
assertTrue(green.equals(blue));
assertTrue(red.equals(blue)); // fails

However, EqualsVerifier doesn't fail on this.

Original issue reported on code.google.com by jan.ouw...@gmail.com on 16 Feb 2013 at 7:45

[GoogleCodeExporter]

This has been fixed in version 1.2. Also, I've blogged about the solution:

* http://www.jqno.nl/post/2013/02/17/reaction-to-cedric-beusts-equals-challenge/
* http://www.jqno.nl/post/2013/03/26/on-transitivity/

Original comment by jan.ouw...@gmail.com on 26 Mar 2013 at 6:57

• Changed state: Fixed
• Added labels: ****
• Removed labels: ****